Weekly archive
LRDigestWeekly digests of little red dots and JWST-selected AGN papers, with curated reading notes and archive pages.
654 indexed papers · 430 research notes
MINERVA/MIRI identifies el Ascua at z~3.8 as a mid-IR-dominant, X-ray-undetected Compton-thick AGN candidate. UV-to-radio SED fitting indicates rapid black-hole growth and a probable AGN radio excess, but obscuration and radio-loudness remain indirect inferences.
Einstein Probe observations of six z≈0.3 local LRD analogs find an X-weak subgroup whose stacked soft-X-ray constraints favor modest intrinsic coronal weakness plus Compton-thin absorption, rather than the specific unobscured super-Eddington or local Compton-thick geometries tested.
High-cadence monitoring of one Seyfert changing-look episode finds that NGC 3227’s continuum and broad Hβ dimmed sharply yet retained a 6–8-day reverberation lag, supporting an inner, high-column obscurer rather than ordinary stochastic accretion variability.
AO-assisted ERIS/SPIFFIER spectroscopy of 34 Gaia Multi-Peak candidates resolves six sub-arcsecond dual AGN and seven lensed quasars, but foreground-star superpositions dominate the non-multiple outcomes and broad-line velocity offsets do not securely measure systemic pair velocities.
In 865 ks of Chandra imaging, no X-ray AGN is detected among 21 confirmed non-quasar members of the z=6.63 J0910−0414 protocluster. The resulting limits do not establish environmental enhancement, but still allow substantial excess activity.
In Simba, apparently molecular-gas-rich recently quenched galaxies can reflect dust-hidden star formation, a low CO–H2 conversion factor, or temporary quiescence. The model favors no single explanation; rejuvenation is high-redshift-weighted and comparatively uncommon.
In SDSS fibre spectra of 1,541 type-1 and 688 type-2 QSOs at z=0.4–0.5, broad NLR components are more blueshifted in type 1s, consistent with orientation-dependent visibility of faster ionised outflowing gas, but energetics remain model-sensitive.
Separate Chandra spectra of the two lensed X-ray emitters in MG B2016+112 support the authors’ dual-AGN interpretation: the inner-caustic component is intrinsically absorbed, disfavoring its alternative identification as a highly magnified jet feature.
JWST/MIRI F770W selection and volunteer classifications of 14,657 PRIMER galaxies at 1<z<3 reveal morphology trends unlike optical/near-IR samples, while wavelength-dependent structure and unresolved mid-IR cores complicate physical interpretation.
SN Helios is a spectroscopically confirmed, strongly lensed Type II supernova at z=3.34. Its predicted 2–6 yr reappearance could enable time-delay cosmography, but current lens-model spread and the absence of a measured delay preclude an H0 result.
Using JWST mid-infrared IFS of NGC 5728, the authors decompose blended circumnuclear line emission into a star-forming ring and AGN bicone. Stacking twelve tracers yields spatial flux fractions that are stable across tested weighting choices.
Mock JWST selection in AMBRA suggests LRDs are transient appearances of existing black hole–galaxy systems: dim sources require a gas-enshrouded AGN model, while massive compact hosts yield longer-lived phases. Redshift counts remain model-sensitive.
Deep JWST/NIRSpec spectra of two luminous LRDs resolve Hα–Hδ absorption near systemic velocity, with higher-order troughs redder and unexpectedly persistent. Broad metal lines and diagnostic ratios favor dense gas, while a stratified failed wind remains an interpretation rather than a detection.
JWST MIRI/Spitzer hydrogen-line measurements in 27 dusty z~1–2 infrared galaxies yield directly inferred nebular attenuation declining from ~3 mag near 2 μm to ~1 mag near 4 μm, yet IR-based SFRs remain ~2.5 times higher.
This theory paper proposes that gas inflow compresses self-interacting dark matter (SIDM) around a pre-existing black hole while an optically thick nuclear disk obscures and reprocesses its emission. It reproduces two representative LRD continua, but does not establish SIDM observationally.
For 142 optically unobscured, FIR-bright Stripe 82 quasars at z=1–4, ALMA deblending lowers inferred host SFRs yet leaves extreme starbursts. The authors find weak instantaneous starburst–accretion coupling and UV-line differences consistent with a transitional interpretation.
Two-stage simulations and radiative-transfer spectral modeling suggest that LRDs could be direct-collapse black-hole hosts whose dense disks trap X-rays and generate Balmer absorption; fits spanning z=3.55–9.29 make this physically plausible, but not uniquely established.
Ultra-deep JWST/SPURS rest-UV spectra of four UV-bright Little Red Dots find dense, nitrogen-enhanced, neutral-gas-embedded nuclei and diverse broad-line/wind signatures. The authors infer compact nuclear activity, while stellar and AGN contributions remain degenerate.
Deep JWST/NIRSpec spectra of nine z=3–6 LRDs favor electron-scattering-like broad-line profiles in five cases, implying substantial ionized columns but ∼50% covering fractions; this challenges unity-covering cocoon models while supporting an AGN-related origin.
RUBIES-EGS-9809 is a single, heavily obscured broad-line AGN host at z=5.7 whose resolved Balmer break and declining-SFR SED fit make it a quenching candidate, not a confirmed post-starburst. Outflow signatures make AGN feedback plausible but unproven.
A disk-plus-dichroic-transmission model can reproduce the ∼1.5% optical continuum and ∼0.7% broad-Hα polarization of the local LRD analog J1025+1402, but the spectropolarimetry constrains continuum polarization more directly than accretion rate or inclination.
JWST spectra of the single dusty galaxy AzTEC-1 at z=4.3419 reveal a broad Hα component blueshifted by 1245 km s⁻¹. The authors favor a candidate sub-pc SMBH binary or recoiling SMBH over an ionized outflow, but confirmation requires resolved follow-up.
A WISE pilot search finds two extreme mid-infrared AGN flares, modeled as dust echoes and interpreted as candidate TDEs. Their high inferred energies and contrasting optical/spectroscopic behavior make them promising, but not definitive, disruptions in active nuclei.
This modelling study proposes tidal-disruption and quasi-periodic-eruption event rates as population-level probes of LRD black-hole masses. Its predictions depend strongly on assumed stellar cusps, black-hole–stellar-mass relations, and the possibility that most LRDs are obscured.
This strategic report argues that Lynx-class subarcsecond, high-throughput X-ray imaging spectroscopy would test why JWST little red dots are X-ray weak, while simulations illustrate broader gains for feedback, accretion, and circumgalactic-gas studies.
In 89 LRDs and 191 LBDs, LRDs have more luminous and broader Hα, larger Balmer decrements, and lower [O III]/Hβ. The authors argue these population-level differences strain luminosity-independent orientation alone, while not uniquely establishing a gas-cocoon mechanism.
In 20 LRDs, extreme broad Balmer decrements require both dense, optically thick non-Case-B line formation and—when Hα/Hβ exceeds the model ceiling—additional broad-line-region-associated dust, rather than galaxy-wide extinction alone.
Using a Soltan-normalized black-hole accretion history and a gas-dynamical upper envelope, the authors find black-hole horizons dominate cosmic entropy production but operate 4–7 dex below their proposed maximum at z=4–12.
Using GOODS-S JWST SMILES+JADES photometry and CIGALE fits, the authors report that obscured-AGN incidence and infrared contribution rise toward high redshift, but are consistent with no systematic dependence on total infrared luminosity within their uncertainties.
JADES-GS 209777 (“the Hatchling”) is a z=3.711 red quasar with exposed broad-line/X-ray emission yet nuclear absorption and multiphase disturbed gas. The authors interpret this combination as a partially cleared, dusty buried-quasar phase.
In one extreme z~6 halo, simulations predict that earlier seeding plus mildly super-Eddington growth drives cold, fast, neutral CGM clumps and extended Hα after feedback clears nuclear sightlines; this is a model prediction, not a population measurement.
JWST/NIRSpec and ALMA resolve LID-1166 into two accreting, gas-associated nuclei separated by ~1.5 kpc at z~4.5. The authors interpret the system as an obscured, gas-rich late-stage merger undergoing super-Eddington SMBH growth.
Using X-ray spectra of the single nearby, long-quenched galaxy KUG 1208+386, the authors report a ≈0.07c nuclear ultra-fast outflow. Its ≥3σ trial-corrected line evidence makes feedback in a quiescent host plausible, but not yet a demonstrated maintenance mechanism.
MEOW uses JWST/MIRI hot-dust selection over GOODS to identify 16 z≳5 AGN candidates, mostly not previously selected as broad-line AGN. Its luminosity-function comparison suggests an obscured population comparable in abundance to broad-line AGN near log Lbol≈45, but faint-end constraints remain limited.
This is a proposed ELT/VESPER integral-field program, not a feedback detection: it will map eleven z=1.5–2.5 obscured, starbursting radio AGN to test whether spatially resolved jet–ISM associations coincide with shocks, outflows, and altered star formation.
This paper uses spatially resolved CIGALE SED fitting to separate the ∼1 kpc nuclear core of GN20 from the full 9.9 kpc galaxy, combining JWST NIRCam, MIRI, NIRSpec PRISM pseudo-continuum, HST, and millimeter data. The central result is that the galaxy-wide SED is overwhelmingly star-formation powered, with only a marginal integrated AGN fraction of 0.09 ± 0.02, while the nucleus requires a much stronger AGN contribution of 0.34 ± 0.05 to explain a rest-frame 2.5–3.6 μm mid-infrared excess from torus-heated dust. That means the AGN contributes about one-third of the nuclear infrared luminosity but only about 9% of the total L_IR, naturally explaining why integrated diagnostics and earlier Spitzer limits made the source look starburst-dominated. The broader significance is that GN20 looks like a buried-black-hole case where only JWST-resolution, nuclear-scale decomposition can uncover ongoing early SMBH growth inside an extreme z = 4.055 dusty starburst.
This forecasting study argues that multi-frequency SKAO continuum observations could separate intrinsically weak, Compton-thick, and ionized-cocoon interpretations of radio-faint JWST AGN and LRDs, but it presents sensitivity-based predictions rather than new radio detections.
JWST/MIRI PCA tomography recovers 11.3-μm PAH velocity maps in three of five z~0.1 type-2 quasars; all three show dust-traced outflow kinematics, with molecular-gas residuals consistent with outflow after disk subtraction.
Monte Carlo torus calculations predict that metal-poor, Compton-thick AGN can transmit more X-ray flux than solar-metallicity counterparts, potentially aiding z≳10 detection. The result is model-based: geometry, viewing angle, abundance pattern, and cold-gas assumptions remain consequential.
Narrow-line ratios in roughly 20 high-S/N JWST/NIRSpec LRD spectra challenge a uniformly opaque, unity-covering gas envelope: at least 40% require extreme ionization conditions, while weak He II indicates an ionizing spectrum softer than standard AGN.
In 36 GOODS LRDs/LBDs at z=2.26–7.89, the authors find AGN-like narrow-line excitation, extreme X-ray weakness, and LRD Lyα excess with a broad component resembling Hα. They argue against completely enclosing cocoon geometries, while retaining obscured-LBD interpretations.
In 65 PRIMER-UDS post-starbursts at z=1–2, massive systems mostly lack mid-IR excess: template tests place population-level obscured accretion below 1% Eddington. Low-mass PSBs instead show 18-μm excess plausibly associated with residual star formation.
Swift eclipse monitoring of ESO 362-G18 uses time-resolved absorption changes to constrain an X-ray source within ~35 Rg. The authors infer a structured cloud and a soft-excess region ~50% larger than, yet overlapping, the hot corona.
KOOLS-IFU maps of NGC 6552 find broad [O III] emission declining with radius but no significant full-sample association between local kinematics and [O III]/Hβ excitation, favoring spatial dynamical structure over a detected excitation–kinematics coupling.
In 412 Stripe 82 Type 2 AGNs, optical RMS variability anticorrelates with several narrow-line luminosities, equivalent widths, and widths. The authors interpret this as variability retaining information about obscured accretion, although controls and photometric-noise limits temper causal inference.
Radiative-transfer models and three illustrative spectra support a hypothesis that little blue dots are lower-column, gas-cocooned AGN related to little red dots. Balmer-jump offsets are suggestive, but population-level fitting and discriminating tests remain outstanding.
Using X-ray spectra and infrared-informed absorption priors, the authors infer that Compton-thick AGN comprise 17% of AGN at z=3–6. The revision sharply reduces candidate classifications, but supports no significant redshift evolution in this fraction.
JWST/NIRSpec IFU spectroscopy of six z~6 SHELLQs narrow-Lyα candidates finds secure broad Balmer components in two, while extended, largely non-rotating ionized gas characterizes several non-broad-line systems. Broad-line incidence rises sharply with Lyα luminosity.
Spatially resolved JWST, ALMA and KCWI data support a multiphase, minor-axis biconical outflow in the dusty local merger IRAS F01364-1042. The authors infer faster ionized than molecular gas and argue a nuclear starburst can energetically drive it despite an obscured AGN.
Forecasts suggest [Ne V] line-intensity-map–galaxy cross-correlations could statistically recover roughly 10% of cosmic-noon AGN line emission from sources below a CDIM-like direct-detection limit, though inference of the faint emissivity remains luminosity-function dependent.
JWST/NIRSpec spectroscopy of 14 LRDs separates Balmer emission and absorption, favoring dense broad-line gas over dust as the main origin of elevated broad Balmer decrements. A clumpy, viewing-angle-dependent nuclear geometry is proposed, but velocity-profile fits succeed in only three of five high-S/N sources.
This theoretical study proposes that collapsed, dark-matter-powered supermassive dark stars can leave massive, inflatable envelopes around prompt black holes, producing cool, optically thick quasi-star-like sources compatible with many Little Red Dot properties; it does not fit an LRD sample directly.
Using simulation-based inference on a synthetic local AGN population, the authors find an intrinsic Compton-thick fraction of 40±3%. Their radiation-regulated geometry broadly reproduces several X-ray observables, but depends materially on fixed, simplified broad-line-region and torus assumptions.
Sirocco cocoon models suggest that current LRD X-ray non-detections require both moderately enriched, Compton-thick gas and intrinsically X-ray-weak/soft AGN emission. The inference is conditional on assumed intrinsic SEDs, metallicities, columns, and redshift-dependent observing bandpasses.
JWST/MIRI-MRS-informed SED fits to the single z=4.601 Hot DOG W2246-0526 favor an added hot-dust component interpreted as polar dust. This changes inferred AGN luminosity, but its geometry and physical association with an outflow remain model-dependent.
A forward model treating little red dots as dust-intercepted, inclined counterparts of compact broad-line AGN matches the currently measured UV luminosity function, but dust covering fraction and cloud extinction remain substantially degenerate.
For the single $M_\star\sim10^{10}\,M_\odot$ host GAMA 376183, NuSTAR and multiwavelength data support a heavily obscured, rapidly accreting AGN in a disturbed system; the proposed merger-triggered starburst/accretion connection remains suggestive rather than demonstrated.
JWST IFU spectroscopy of NGC 7582 separates rotating circumnuclear-disk gas from an AGN bicone by ionisation potential and line-profile decomposition, finding distinct kinematic axes and broader outflow lines; mixed-ionisation tracers require two components.
Deep NOEMA observations of three z>6 JWST AGN—two Little Red Dots and one blue Type-I source—yield no significant [C II] or dust-continuum detection, tightening host-galaxy and SED constraints while leaving the physical origin of their [C II] deficit unresolved.
A reanalysis of UHZ1’s full Chandra exposure and new MIRI non-detections reduces the evidence for its proposed luminous, Compton-thick direct-collapse black hole: the X-ray excess is marginal and non-persistent, while infrared limits exclude the originally inferred luminosity scale.